In a time division duplex (TDD) system, receiving and sending are completed at different time of a same frequency band, that is, an uplink and a downlink are differentiated in terms of time. A Long Term Evolution (LTE) system can support seven different uplink-downlink subframe configurations. In a system before LTE Rel-12, all user equipments (UE) in a cell are notified of a specific used uplink-downlink subframe configuration by using a broadcast message SIB 1, while in a Rel-12 system, all UEs in a cell are notified by using a physical control channel (PDCCH), and in Rel-12, an uplink-downlink subframe configuration actually used by a UE may be different from an uplink-downlink subframe configuration indicated in a SIB 1. In the Rel-12 system, an uplink-downlink subframe configuration used by a UE may be changed within a short period of time, for example, may be changed within a time period of 10 ms, and in the Rel-12 system, such a manner of quickly changing uplink-downlink subframe configuration information is referred to as dynamic TDD subframe configuration.
When dynamic TDD subframe configuration is used in the TDD system, different changes may occur in uplink-downlink subframe configurations of a local cell and a neighboring cell. In this case, a downlink subframe of the local cell may be interfered with by an uplink subframe from the neighboring cell, an uplink subframe of the local cell may also be interfered with by a downlink subframe of the neighboring cell, and the two types of interference are both referred to as contradirectional interference. Conversely, an uplink subframe from the neighboring cell may cause interference to an uplink subframe of the local cell, or a downlink subframe of the neighboring cell may cause interference to a downlink subframe of the local cell, and the two types of interference are both referred to as codirectional interference. As shown in FIG. 1, according to a difference in interference from a neighboring cell, downlink subframes 0, 1, 3, 5, 6, and 8 (which are marked as X) of a local cell may be grouped into a first subframe set, downlink subframes 4 and 9 (which are marked as F) may be grouped into a second subframe set, and U represents an uplink subframe. In a wireless communications system such as an LTE or an advanced Long Term Evolution (LTE-A) system, to improve transmission efficiency of the system and improve quality of service of a UE, the UE needs to measure channel state information (CSI) and reports the CSI to a base station device. CSI reporting includes periodic CSI reporting and aperiodic CSI reporting. A base station device configures an aperiodic CSI reporting mode in a semi-static manner by using higher layer signaling, and triggers aperiodic CSI reporting by using physical layer signaling. After receiving aperiodic CSI triggering signaling, user equipment reports aperiodic CSI. A timing relationship between an aperiodic CSI triggering subframe and a reporting subframe N is determined according to timing of an uplink reference subframe configuration.
In the prior art, a subframe of an available CSI measurement subframe resource needs to be located between an aperiodic CSI triggering subframe and reporting subframes N−4. As shown in FIG. 2, a subframe 0 triggers a subframe 7 to report aperiodic CSI, and therefore, a CSI measurement subframe may be located in a subframe 0, 1, or 3, where a subframe 2 is an uplink subframe. Similarly, a subframe 5 triggers a subframe 12 to report aperiodic CSI, and therefore, a CSI measurement subframe may be located in a subframe 5, 6, or 8, where the subframe 7 is an uplink subframe. According to the example of downlink subframe grouping in FIG. 1, it can be seen that the subframes 0, 1, 3, 5, 6, and 8 all belong to the first subframe set. Therefore, regardless of which downlink subframe is used for triggering, CSI measurement of the second subframe set cannot be performed. As a result, aperiodic CSI of the second subframe set cannot be reported.
A solution in the prior art is that: if there is no resource that can be used for measurement in a corresponding subframe set, aperiodic CSI information corresponding to the subframe set is not reported, or a piece of latest recorded CSI information of a corresponding subframe is reported. As shown in FIG. 2, because there is no CSI measurement subframe resource in the second subframe set, after receiving a corresponding aperiodic CSI triggering indication, a UE may report (out of range, OOR) information and may not report aperiodic CSI, or may report a last piece of available aperiodic CSI measurement information. Such a manner causes that a corresponding CSI of the second subframe set cannot be reported.
In conclusion, a problem that aperiodic CSI of some downlink subframe sets in a radio frame cannot be reported needs to be resolved.